How to combine TextMeshPro Font Material with Wiggle Text Shader in Unity?

Question

I have a Unity GameObject with a TextMeshPro component (let's call this object "White Letter"). The Font Material is using the "TextMeshPro/Distance Field" shader. This works perfectly.

I'd like to make the White Letter "wiggle" a bit using a shader (see below). I'd like the effect to look something like this (made using After Effects):

https://www.youtube.com/watch?v=HUmzcU8llPQ

Here's how I combined my Font Material together with this WiggleTextDF Shader:

• I created a WiggleTextDF shader.
• I created a WiggleTextDF Material and set the shader to WiggleTextDF shader.
• I added a Displacement Map and Texture to the WiggleTextDF Material (here they are):

• Finally, I applied this Material (as Element 0) to the Mesh Renderer for the White Letter GameObject.

Every time I do that last step... the font stops rendering and the TextMeshPro renders as a pink box.

Any advice on how to move forward?

Shader "WiggleTextDF" {
Properties {
    _MainTex ("Texture", 2D) = "white" {}
    _DisplacementMap ("Displacement Map", 2D) = "white" {}
    _WiggleAmount ("Wiggle Amount", Range(0, 1)) = 0.1
    _WiggleSpeed ("Wiggle Speed", Range(0, 10)) = 5
}
SubShader {
    Tags {"Queue"="Transparent" "RenderType"="Transparent"}
    Pass {
        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #include "UnityCG.cginc"
        #include "UnityTextMeshPro.cginc"

        struct appdata {
            float4 vertex : POSITION;
            float2 uv : TEXCOORD0;
            UNITY_VERTEX_INPUT_INSTANCE_ID
        };

        struct v2f {
            float2 uv : TEXCOORD0;
            UNITY_VERTEX_OUTPUT_STEREO
            float4 vertex : SV_POSITION;
        };

        sampler2D _MainTex;
        sampler2D _DisplacementMap;
        float _WiggleAmount;
        float _WiggleSpeed;

        v2f vert (appdata v) {
            v2f o;
            UNITY_SETUP_INSTANCE_ID(v);
            UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
            o.vertex = UnityObjectToClipPos(v.vertex);
            o.uv = v.uv;
            return o;
        }

        fixed4 frag (v2f i) : SV_Target {
            UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(i);
            UNITY_SETUP_INSTANCE_ID(i);
            // Sample the displacement map texture to get the displacement value
            float4 displacement = tex2D(_DisplacementMap, i.uv);

            // Calculate the wiggle offset based on the displacement value and time
            float2 wiggleOffset = sin(_Time.y * _WiggleSpeed + i.uv * 10) * displacement.rg * _WiggleAmount;

            // Apply the offset to the texture coordinates
            float2 uv = i.uv + wiggleOffset;

            // Sample the main texture using the offset texture coordinates
            fixed4 col = tex2D(_MainTex, uv);

            UNITY_APPLY_FOG_COLOR(i.fogCoord, col);
            return UNITY_PREPARE_FINAL_COLOR(col);
        }
        ENDCG
    }
}
FallBack "TextMeshPro/Distance Field"

}